src/tools.rs - file_set_contents_full: only call fchmod when we pass permissions

So that we can use it to write into /etc/pve/ (which does not support chmod).

src/tools.rs

@@ -197,10 +197,12 @@ pub fn file_set_contents_full<P: AsRef<Path>>(
         stat::Mode::S_IRGRP | stat::Mode::S_IROTH
     ));
 
+    if perm != None {
         if let Err(err) = stat::fchmod(fd, mode) {
             let _ = unistd::unlink(tmp_path);
             bail!("fchmod {:?} failed: {}", tmp_path, err);
         }
+    }
 
     if owner != None || group != None {
         if let Err(err) = fchown(fd, owner, group) {